While most of the NFL offseason talk will center on April's draft, all 32 teams are sure to improve or decline through free agency this coming spring.

With a number of big-name players facing uncertain futures as their contracts expire, some others are flying under the radar. But that doesn't mean they aren't elite weapons capable of boosting an NFL team in 2013.

Here, we'll showcase a trio of top under-the-radar free-agent stars.

Jared Cook, TE

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A four-year NFL veteran, tight end Jared Cook has made a name for himself with the Tennessee Titans in recent seasons, developing into one of the league's more sure-handed pass-catchers.

Cook will be a coveted free agent this offseason because of his above average play-making ability and his age. He's only 25 years old and won't turn 26 until April. At 6'5", 250 pounds, the former South Carolina Gamecock is also one of the more athletic tight ends available this year.

Cook has caught 131 balls in 59 career regular-season games, turning out 81 first downs and eight touchdowns.

He is more than just a big chain-moving target, though. Cook has deceptive speed and can get behind the defense if given the time to do so.

Rashard Mendenhall, RB

Injuries are a concern with Rashard Mendenhall, but like Cook, he's only 25 and has produced in the not-so-distant past. In 2009 and 2010, he rushed for over 1,100 yards while playing in all 16 regular-season games for the Pittsburgh Steelers.

His career 4.1 yards-per-carry average isn't going to propel him to the Hall of Fame, but it does speak to his consistency.

In addition to carrying the rushing load, Mendenhall is a shifty receiver out of the back field and can serve as an excellent dump-down option in passing situations. He averages 8.6 yards per reception for his NFL career.

NFL running backs hold value in their youth, and Mendenhall is just reaching his prime, assuming he can stay healthy.

Greg Jennings, WR

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With Dwayne Bowe, Danny Amendola, Wes Welker, Mike Wallace and Brian Hartline all set to become free agents this offseason, one could argue that Greg Jennings is flying under the radar after a quiet season in Green Bay.

Before 2012, Jennings had been one of the league's most durable wideouts. But after getting banged up this past season with the Packers, many teams will wonder about the state of his body as he nears age 30.

Despite the risk, whoever signs Jennings will be getting a precise route-runner with a great set of hands.

From 2008 to 2010, Jennings recorded three straight 1,100-plus yard receiving seasons and has reeled in more than 50 touchdowns during his first seven NFL season with Green Bay.

He may not be a speed merchant at this point in his career, but he's an intelligent veteran and a playmaking threat nonetheless. Those traits make him one of the top available weapons flying under the radar this offseason.